Chimney install - framing roof joists

[Grif]

Hey all,

I've been lurking here for the last few months and am nearly finished with my stove and chimney installation project. I have a question about my chimney. I went with SuperVent class A chimney from Menards. According to the instructions, I need to frame (all four sides) the opening in my attic where the chimney enters from the roof. I understand the need to frame where the attic insulation shield is supported, but I can't think of a benefit to framing around the chimney at the ceiling joists. What am I not seeing here?

The instructions are located here: http://www.selkirkcanada.com/supervent/Product.aspx?id=220&ekmensel=c580fa7b_46_48_220_1
Then click on Installation --> View Documents --> SuperVent USA Instructions
Look down to figure 4 on page 5.

Thanks for your help, folks!

Nick

 

[Metal]

That is how it was tested at UL, so that is how it needs to be installed. How much does three feet of 2x4 and some nails cost anyway?

 

[Tfin70]

The only reason I can think of for framing on the roof joists is if you needed to cut one out of the way, then you'd obviously want to re-frame. Beyond that I can't think of a good reason (other than "thats the way it was tested").

I just installed a Simpson Duro Vent double wall class A insulated chimney. But they only called for framing around the celing support box. I was lucky, my chimney came up exactly between my two trusses.

 

[Grif]

I don't mind doing it - it'll take me 5 minutes. I'm going to end up doing it. It's just that I would like to understand why I'm doing it!

Thanks,
Grif

 

[Tfin70]

Oh I understand, I'm the same way. Good luck with your install.

 

[Metal]

Most companies don't require it (and it does seem silly), but ya gotta do what ya gotta do.

 

[JimWalshin845]

Don't forget that flue is gong to need flashing around it and you want something good besides plywood to nail into it.

 

[nshif]

In the 1st place they arnt roof joists they are rafters or trusses. Trusses should never be cut. nor should rafters but you can get away with it ( not sure about code here ) I beleive their diagram pretains to cutting them. Its better to go between them with offsets in the pipe. With my simpson I only framed in the bottom chord of the trusses and the flashing was attached to the trusses.

 

[JimWalshin845]

YEP.... and it is only going to take him "5 minutes" to do the job. Geesh, it would take me 5 minutes to lineup where I am going to screw up first!! >:-(

 

[JohnnyBravo]

i cut my truss out and it took more than five minutes but it was worth it, the stove is where i want, the chimney is straight and my roof is not going fall on anyones head.

the framing around the four sides is to attach the ceiling suport, the suport is rated for 40' of chimney or something stupid like that.

 

[JimWalshin845]

Hopefully Santa or his reindeer don't land close to the flue. And we all know snow loads are nothing to deal with in AB Canada. OOOOOPs... I forgot... there is no pitch to that roof.

5 Minutes of thought,
J&K;

 

[JohnnyBravo]

Hopefully Santa or his reindeer don't land close to the flue. And we all know snow loads are nothing to deal with in AB Canada. OOOOOPs... I forgot... there is no pitch to that roof.

5 Minutes of thought,
J&K;

huh? no pitch? we do get some snow. snow load should not be a problem, santa on the other hand is one fat man.

 

[Gooserider]

Don't know, but my guess is that since you are cutting a hole in the roof sheathing, they want to be sure it's supported all the way around the hole. It seems more logical that they would require it than that the other companies wouldn't....

This is just gut instinct though, not specific expertise.

Gooserider

 

[JimWalshin845]

Hopefully Santa or his reindeer don't land close to the flue. And we all know snow loads are nothing to deal with in AB Canada. OOOOOPs... I forgot... there is no pitch to that roof.

5 Minutes of thought,
J&K;

huh? no pitch? we do get some snow. snow load should not be a problem, santa on the other hand is one fat man.

I am glad you amended/edited ;-P your original post and added.

"the framing around the four sides is to attach the ceiling suport, the suport is rated for 40’ of chimney or something stupid like that.";

Things are good. :coolmad:

 

[James04]

Ill try this again. Some how my post never made it.

I thought the same as you (why). However, I came to the conclusion that if you use full width bocking you will prevent the chimney chase from drawing warm air out of the house through the ceiling joist bays. weather in the attic or a lower level ceiling.

James

 

[JimWalshin845]

Ill try this again. Some how my post never made it.

I thought the same as you (why). However, I came to the conclusion that if you use full width bocking you will prevent the chimney chase from drawing warm air out of the house through the ceiling joist bays. weather in the attic or a lower level ceiling.

James

Roof joists have to 'breathe' or your roof decking will delaminate and shingles will become crispy.

Yes, you do have to put cross members across the roof trusses but it is for structural purposes and possibly to hang brackets for the new flue besides being able to nail the flashing cap down.

 

[elkimmeg]

i cut my truss out and it took more than five minutes but it was worth it, the stove is where i want, the chimney is straight and my roof is not going fall on anyones head.

the framing around the four sides is to attach the ceiling suport, the suport is rated for 40' of chimney or something stupid like that.

please be advised is not recommended to cut trust a definite code violation If you have to cut a ceiling joist or rafter the next adjoining ones have to be doubled up and headed off to transfer the weight / support of the one cut

 

[JimWalshin845]

i cut my truss out and it took more than five minutes but it was worth it, the stove is where i want, the chimney is straight and my roof is not going fall on anyones head.

the framing around the four sides is to attach the ceiling suport, the suport is rated for 40' of chimney or something stupid like that.

please be advised is not recommended to cut trust a definite code violation If you have to cut a ceiling joist or rafter the next adjoining ones have to be doubled up and headed off to transfer the weight / support of the one cut

And I beleive they must be installed with T-Gel hangers.

 

[KeithO]

Nick

I've just done a similar install. In my case I used a cathedral ceiling radiation shield even though I had a flat ceiling. It was 12x12" square so one frames it in structurally. In my case the weight of the class A is carried by the the radiation shield box. There is a strap around the Class A in the box that is screwed to the class A with 4 sheet metal screws and of course the strap is tight around the class A to begin with. The flashing in the roof serves as a guide and then I have 2 stays bracing the upper 3 ft of the class A above the roof. The stays have to be anchored back to the roof trusses, not simply bolted to the sheething. I accomplished this with 2 custom made angle brackets. The stays are sold with pathetic pipe clamps, I ditched them and drilled a 1/4" hole through both pipes and bolted mine. They sure won't be going anywhere...

Where abouts are you ? I'm just south of Big Wolf lake near Napoleon.

Keith

Hey all,

I've been lurking here for the last few months and am nearly finished with my stove and chimney installation project. I have a question about my chimney. I went with SuperVent class A chimney from Menards. According to the instructions, I need to frame (all four sides) the opening in my attic where the chimney enters from the roof. I understand the need to frame where the attic insulation shield is supported, but I can't think of a benefit to framing around the chimney at the ceiling joists. What am I not seeing here?

The instructions are located here: http://www.selkirkcanada.com/supervent/Product.aspx?id=220&ekmensel=c580fa7b_46_48_220_1
Then click on Installation --> View Documents --> SuperVent USA Instructions
Look down to figure 4 on page 5.

Thanks for your help, folks!

Nick

 

[Tfin70]

I don't know, my Simpson chimney kit didn't require me to frame a box around where the chimney penatrates the roof. However I try to follow the manufacturer's instructions to a T.

I used beefy stainless steel screws to secure the roof flashing instead of nails, so I feel pretty good about the flashing not going any where.

I did cut two pieces of truss out of the way (not the entire truss), but re-framed them once I was finished with the install.

 

[JohnnyBravo]

i cut my truss out and it took more than five minutes but it was worth it, the stove is where i want, the chimney is straight and my roof is not going fall on anyones head.

the framing around the four sides is to attach the ceiling suport, the suport is rated for 40' of chimney or something stupid like that.

please be advised is not recommended to cut trust a definite code violation If you have to cut a ceiling joist or rafter the next adjoining ones have to be doubled up and headed off to transfer the weight / support of the one cut

yeah, i know. i have a structural engineer on a beer retainer. you should see the beem work and hangers that are up there. it was a pain because i refused to drop the ceiling. i have a 4/12 pitch and my chimney is about 3' in from the pitch, there was not much head room in there. i would not recomend that any one cut there truss unless they know what they are doing. i drew up my plan and my friend came over and did all the caulclations. the cut truss is now suported by beam bearing on a wall and on a pair of trusses eight feet over one of which is doubled up on the top and bottom cords and its also sheetedon the other side.

 

[Grif]

Thanks everybody for your help. I did the framing job last night and am waiting for a dry day where I can go up on the roof and finish installation of the roof guy kit. I should be burnin' in my Quad 3100 by this weekend!

KeithO - I'm up in Plainwell, Michigan (North of K-zoo).

Happy Thanksgivin'.

~Nick

 

[Metal]

Don't forget to take/post pics. Good luck!